Abstract We present a multiwavelength photometric and spectroscopic analysis of 13 super-Chandrasekhar-mass/2003fg-like Type Ia supernovae (SNe Ia). Nine of these objects were observed by the Carnegie Supernova Project. The 2003fg-like SNe have slowly declining light curves (Δ m 15 ( B ) < 1.3 mag), and peak absolute B -band magnitudes of −19 < M B < −21 mag. Many of the 2003fg-like SNe are located in the same part of the luminosity–width relation as normal SNe Ia. In the optical B and V bands, the 2003fg-like SNe look like normal SNe Ia, but at redder wavelengths they diverge. Unlike other luminous SNe Ia, the 2003fg-like SNe generally have only one i -band maximum, which peaks after the epoch of the B -band maximum, while their near-IR (NIR) light-curve rise times can be ≳40 days longer than those of normal SNe Ia. They are also at least 1 mag brighter in the NIR bands than normal SNe Ia, peaking above M H = −19 mag, and generally have negative Hubble residuals, which may be the cause of some systematics in dark-energy experiments. Spectroscopically, the 2003fg-like SNe exhibit peculiarities such as unburnt carbon well past maximum light, a large spread (8000–12,000 km s −1 ) in Si ii λ 6355 velocities at maximum light with no rapid early velocity decline, and no clear H -band break at +10 days. We find that SNe with a larger pseudo-equivalent width of C ii at maximum light have lower Si ii λ 6355 velocities and more slowly declining light curves. There are also multiple factors that contribute to the peak luminosity of 2003fg-like SNe. The explosion of a C–O degenerate core inside a carbon-rich envelope is consistent with these observations. Such a configuration may come from the core-degenerate scenario.
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Analyzing Type Ia supernovae near-infrared light curves with principal component analysis
Thermonuclear explosions of C/O white dwarf stars in binary systems known as Type Ia supernovae (SNe Ia) remain poorly understood. The complexity of their progenitor systems, explosion physics, and intrinsic diversity poses challenges in understanding these phenomena as astrophysical objects, as well as their standardization and use as cosmological probes. Near-infrared (NIR) observations offer a promising avenue for studying the physics of SNe Ia and for reducing systematic uncertainties in distance estimations, as they exhibit lower dust extinction and smaller dispersion in peak luminosity than optical bands. In this work, we applied a principal component analysis (PCA) to a sample of SNe Ia with well-sampled NIR (YJH-band) light curves to identify the dominant components of their variability and constrain physical underlying properties. The theoretical models are used for the physical interpretation of the PCA components, where we found that the56Ni mass best describes the dominant variability. Other factors, such as mixing and metallicity, were found to contribute significantly as well. However, some differences are seen among the components of the NIR bands, which could be attributed to differences in the explosion aspects they each trace. Additionally, we compared the PCA components to various light curve parameters, identifying strong correlations between the first component inJandHbands (second component inY) and peak brightness in both the NIR and optical bands, particularly in theYband. When applying a PCA to NIR color curves, we found interesting correlations with the host-galaxy mass, where SNe Ia with redder NIR colors are predominantly found in less massive (potentially more metal-poor) galaxies. We also investigated the potential for improved standardization in theYband by incorporating PCA coefficients as correction parameters, leading to a reduction in the scatter of the intrinsic luminosity of SNe Ia. As new NIR observations become available, our findings can be further tested, ultimately refining our understanding of SNe Ia physics and enhancing their reliability as cosmological distance indicators.
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- Award ID(s):
- 2306395
- PAR ID:
- 10688909
- Publisher / Repository:
- Springer
- Date Published:
- Journal Name:
- Astronomy & Astrophysics
- Volume:
- 702
- ISSN:
- 0004-6361
- Page Range / eLocation ID:
- A134
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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